Why did Selena Gomez and on-and-off boyfriend Justin Bieber split for good? Find out the real reason here!

According to Life & Style (via HollywoodLife.com), the couple's very last argument caused them to call it quits.

In an effort to save their unstable relationship following their breakup back in October 2014, the Canadian pop star and "The Heart Wants What It Wants" crooner reportedly went to a Tiffany & Co. store in Beverly Hills last December to check out engagement rings.

An eyewitness recalled that when a bystander at the store asked the two if they would get married one day, "Selena said, 'I hope so!'"

On the other hand, Bieber was "mouthing the word 'No,' and he motioned with his hand to his throat like a 'cut it out' sign, while shaking his head."

As a result, the pair allegedly ended up not buying the rings and blew their one last shot.

Following the final breakup, Gomez has seemingly moved on from her ex-boyfriend with Zedd, whom she apparently thinks is "marriage material and perfect dad material."

HollywoodLife.com recently reported that the "I Want You to Know" duo is moving fast and already talking marriage.

"They've talked about kids, and both of them want a big family," a source revealed. "Selena says wherever they go, babies and little kids always gravitate towards Zedd, because he's so silly and fun to be around. Plus, she says he's super patient."

Moreover, in an interview with Radio Disney's Alli Simpson on March 20, Selena Gomez gushed about her latest love interest.

"He's this cute little German, and he's got really beautiful eyes, and he's very sweet and funny," she said.

"I respect his vision, because he has a way of knowing how important his role is an EDM artist, and he doesn't spend most of his time traveling the world DJ-ing," she added. "He's great, and he cares so much about the meaning of his songs."